Why are some drinks served as a double measure ie Baileys Martini Pimms etc and is it legal requirement?

It's not a legal requirement to serve certain drinks as a "double" measure. The practice of serving a "double" is more of a cultural and industry-specific custom, influenced by factors like:

1. Tradition and Consumer Expectation:

* Historical Practices: In some cases, certain drinks have traditionally been served as "doubles." This is often linked to the historical origins of the drink or how it was originally consumed.

* Customer Preference: Many customers, especially those familiar with specific drinks, expect a certain volume or strength. This might be due to personal preference, familiarity, or the perception that a "double" is "stronger" or "more satisfying."

2. Bar/Restaurant Practices:

* Profitability: Serving a "double" can sometimes be more profitable for establishments, as it involves a larger volume of alcohol.

* Standard Operating Procedures: Some bars or restaurants may have established policies on serving specific drinks as "doubles" based on their target audience, menu design, or internal practices.

3. Alcohol Strength and Serving Style:

* Dilution: Some drinks, like cocktails, are already diluted with mixers. Serving them as a "double" allows for a more concentrated flavor and stronger alcohol content.

* Cocktail Culture: "Double" measures might be associated with specific cocktail styles, like a classic Martini or a Manhattan, where the focus is on precise ingredient ratios and strength.

Legality and Regulations:

* No Specific Law: There are generally no specific laws requiring a "double" measure for any particular drink.

* Drink Measures: Licensing regulations typically focus on minimum measures for alcoholic beverages, not specific serving sizes for particular drinks.

* Ethical Considerations: While not legally mandated, ethical bars and restaurants may choose to provide standard measures and clear communication about serving sizes to ensure fair pricing and customer satisfaction.

In Conclusion:

The practice of serving "doubles" is not a legal requirement. It is more about industry norms, customer expectations, and the specific characteristics of individual drinks. It's essential for bars and restaurants to be transparent about their serving practices and ensure customers are informed about the volume and strength of their drinks.